Extended Abstract (116K)6.2
Can possible heavy rainfall events be identified by comparing various parameters to the climatological norms?
Richard H. Grumm, NOAA/NWS, State College, PA; and N. W. Junker, R. Hart, and L. F. Bosart
A 10-year climatology of 4-inch and greater rainfall events was constructed and analyzed over the conterminous U.S. For each case, the mean-sea level pressure and 500 hPa height analysis at 0000 UTC and 1200 UTC were examined to establish which time was most likely closest to the beginning of the event. Gridded fields for these times were then compared to the daily climatological means from the 30-year period from 1961-1990. GRADS (http://grads.iges.org/grads/) was used to compute and plot deviations of selected parameters at standard levels from the 30-year normal each event. The mean-seal level pressure and 500hPa analysis was also plotted. A database has been established to save selected fields in an attempt to establish patterns and anomalies that provide a signature that an heavy rainfall event may be expected. The plots from the different cases will be sorted by type and geographic region to determine whether there are similarities for various types of heavy rainfall events (ie: Maddox frontal, synoptic type events). Plots will also be separated by region. Preliminary findings suggest that most heavy rainfall cases are associated with anomalous specific humidity through a deep layer of the lower troposphere. Many events are also associated with anomalous low-level winds directed from a moisture source towards the location where the event occurred. Three case studies will be discussed: a synoptic type heavy rainfall event, an upslope event along the eastern slopes of the Appalachians and a winter west coast case. The anomaly fields that best characterize each type of event will be shown.
Session 6, Winter Weather and Climatological Studies
Wednesday, 14 August 2002, 8:00 AM-10:00 AM
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